/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * libc/stdio/lib_memsistream.c
 *
 *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <assert.h>

#include "lib_internal.h"

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: memsistream_getc
 ****************************************************************************/

static int memsistream_getc(FAR struct lib_sistream_s *this)
{
	FAR struct lib_memsistream_s *mthis = (FAR struct lib_memsistream_s *)this;
	int ret;

	DEBUGASSERT(this);

	/* Get the next character (if any) from the buffer */

	if (mthis->offset < mthis->buflen) {
		ret = mthis->buffer[mthis->offset];
		mthis->offset++;
		this->nget++;
	} else {
		ret = EOF;
	}

	return ret;
}

/****************************************************************************
 * Name: memsistream_seek
 ****************************************************************************/

static off_t memsistream_seek(FAR struct lib_sistream_s *this, off_t offset, int whence)
{
	FAR struct lib_memsistream_s *mthis = (FAR struct lib_memsistream_s *)this;
	off_t newpos;

	DEBUGASSERT(this);

	switch (whence) {
	case SEEK_CUR:
		newpos = (off_t)mthis->offset + offset;
		break;

	case SEEK_SET:
		newpos = offset;
		break;

	case SEEK_END:
		newpos = (off_t)mthis->buflen + offset;
		break;

	default:
		return (off_t)ERROR;
	}

	/* Make sure that the new position is within range */

	if (newpos < 0 || newpos >= (off_t)mthis->buflen) {
		return (off_t)ERROR;
	}

	/* Return the new position */

	mthis->offset = (size_t)newpos;
	return newpos;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: lib_memsistream
 *
 * Description:
 *   Initializes a stream for use with a fixed-size memory buffer.
 *
 * Input parameters:
 *   instream    - User allocated, uninitialized instance of struct
 *                 lib_memsistream_s to be initialized.
 *   bufstart    - Address of the beginning of the fixed-size memory buffer
 *   buflen      - Size of the fixed-sized memory buffer in bytes
 *
 * Returned Value:
 *   None (instream initialized).
 *
 ****************************************************************************/

void lib_memsistream(FAR struct lib_memsistream_s *instream, FAR const char *bufstart, int buflen)
{
	instream->public.get = memsistream_getc;
	instream->public.seek = memsistream_seek;
	instream->public.nget = 0;	/* Total number of characters read */
	instream->buffer = bufstart;	/* Start of buffer */
	instream->offset = 0;		/* Will be the buffer index */
	instream->buflen = buflen;	/* Length of the buffer */
}
